Supersensitization of photographic silver halide emulsions



Nov. 18, 1958 J. E. JONES 2,860,981

SUPERSENSITIZATION OF PHOTOGRAPHIC SILVER HALIDE EMULSIONS Filed May 21, 1956 LI 511' A/B v kIHI J/HTIHITITTITNJHI llll Hll Ill 300 400 500 e00 100 j A 2 (3,3 4 DICYANOALLYLIDENE) 3 ETHYLBENZOTHIAZOLINE B 2 (3,3 DICYANOALLYLIDENE) '3 ETHYLBENZOTHIAZOLINE WITH PYRIDINE fi q Am llH llll llll llll llll mu m 500 400 1 s00 600. 700

C (5,5 DICYANO 2 ,4 PENTADIENYLIDENE) 3 METHYLBENZO THIAZOLINE D 2 (5,5 DICYANO'2,4PENTADIENYLIDENE 3' METHYLBENZO' THIAZOLINE WITH PYRIDINE E I l E 2 15,5 DICYANO- 2 ,4 PE'NTADIENYLIDENE) l- ETHYL 8 NAPHTHOTHIAZOLINE F 2 (5,5 DICYANO 2,4 PENTADIENYLIDENE) l' ETHYL' NAPHTHOTHIAZOLINE WITH PYRIDINE f JEAN E. JONES INVENTOR.

AT TORNEYS.

SUPERSENSITIZATION OF PHOTOGRAPHIC SILVER HALIDE EMULSIONS Jean E. Jones, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application May 21, 1956; Serial No.'586,053

18 Claims. (Cl. 96-104) This invention relates to photographic silver halidev emulsions containing certain polymethine dyes, and in supersensitizing combination therewith, pyridine bases.

It is known in the art of making photographic emulsions that certain dyes of the cyanine class alter the sensitivity of photographic emulsions of the gelatino-silverhalide kind, when the dyes are incorporated in the emulsions. It is also known that the sensitization produced by a given dye varies somewhat with the typeof emulsion in which the dye is incorporated. Furthermore, the sensitization of a given emulsion by a given dye may be altered by varying the conditions in the emulsion. For example, the sensitization may be increased by increasing the silver ion concentration or decreasing the hydrogen ion concentration (i. e., increasing the alkalinity) or both. Thus, sensitization can be increased by bathing plates, coated with a spectrally sensitized emulsion, in water or in aqueous solutions of ammonia. Such a process of altering the sensitivity of a sensitized emulsion by-increasing the silver ion concentrationand/or-by decreasing the hydrogen ion concentration is commonly.

called hypersensitization. Hypersensitized emulsions have generally poor keeping qualities.

I have now found a new means of altering the sensitivity in emulsions containing cyanine dyes. Since the conditions in the emulsion, i. e., the hydrogen ion and/or the silver ion concentration undergo little or nochange in my method, I shall designate' m'y new method as' a kind of supersensitization.

It is, therefore, an object of my invention to provide photographic silver halide emulsions containing polymethine dyes, and in supersensitizing combination therewith, pyridine bases. Another object is to provide a process for preparing these sensitized emulsions. Other objects will become apparent from a consideration of the following description and examples.

The polymethine dyes 'usefuli in practicing my invention are sometimes referred to asb en-chain merocyanines, and can be represented by the following general formula:

wherein -R represents an alkyl group, such as .methyl, ethyl, propyl, butyl, 'car'b'ethoxymethyl, benzyl (phenylmethyl), etc. (e. g., an alkyl group containing from 1 to 4 carbon atoms), R represents a hydrogen atom or a lower alkyl group, such as methyl, ethyl, etc., R, represents a hydrogen atom, a lower alkyl group, such as methyl, ethyl, etc., a lower alkoxyl group, such as methoxyl, ethoxyl, etc., a monocyclic aryl group, such as phenyl, tolyl, etc., or a heterocyclic group, such as thienyl, and R and R can together represent an alkylene group "ice (ie. we t th y,v s ns m e l kane i such as cyclopentane, cyclohexane, etc.), n represents a positive integer of from 1 to 2, and Z represents the non metallic atoms necessary to complete a heterocyclic nucleus containing from too atoms in the heterocyclic ring, such as those selected from the group consisting of those of the benzothiazole series (e. g., benzothiazole, 4- chlorobenzothiazole, 5 chlorobenzothiazole, 6 chlorobenzothiazole, 7 chlorobenzothiazole, 4 methylbenzothiazole, 5-methylbenzothiazo1e, 6-methylbenzothiazole,, S-bromobenzothiazole, 6-bromobenzothiazole; .4-phenylbenzothiazole, 5-phenylbenzothiazole, 4-methoxybenzothiazole, 5-methoxybenzothiazole, o-methoxybenzothia- 'zole, S-iodobenzothiazole, o-iodobenzothiazole, 4-ethoxybenzothiazole, S-ethoxybenzothiazole, tetrahydrobenzothiazole, 5,6-dimetho iybenzothiazole, 5,6-dio xymethylenebenzothiazole, 5- hydroxybenzothiazole, G-hydroxybenzothiazole, etc.), those of the naphthothiazole series.

(e. g., naphtho[1,2]thiazole, naphtho[2,1]thiazole, 5-

methoxynaphtho {2,1 thiazole, 5 -ethoxynaphtho [2, l thiazole, S-methoxynaphthol1,2]thiazole, 7-methoxynaphtho[1,2]thiazole, etc.), those of the benzoxazole series (e. g., benzoxazole, S-chlorobenzoxazole, 5-methylben zoxazole, 5 phenylbenzoxazole, 6 methylbenzoxazole,

5,6 dimethylbenzoxazole, 4,6-dirnethylbenzoxazole, 5- methoxybenzoxazole, S-ethoxybenzoxazole, S-chlorobem zoxazole, 6-methoxybenzoxazole, ihydroxybenzoxazole, o-hy'dr'oxybenzoxa'zole, 'etc.),Ithose of the naphthoxazole,

' series (e. g., naphtho[1,2]oxazole, naphtho[2,1]oxazole, 1

etc.), those of the benzoselenazole series (e. g., benzoselenazole, S-chlorobenzoseleriazole, S-methoxybenzoselenazole,, S-hydroxybenzoselenazole, tetrahydrobenzoselenazole, etc.), those of the naphtho selenazole series (e. g., naphtho[l,2]selenazole, naphtho2,1] selenazole,

etc.), those of the thiazoline series (e. g., thiazoline, 4- methylthiazoline, etc.), those of the benzimidazoleseries zimidazole, etc.), those of the 3,3-dialkylindolenine series (e. g., 3,-3-dimethylinclolenine, 3,3,5-trimethylindolenine,

3,3,7-trimethylindolenine, etc.), etc.

The pyridine bases useful in practicingmy invention comprise those represented by the following general formula:

group, such as methyl, ethyL'etc; Typical bases include pyridine, oc-, 13-,and 7-picoline, etc.

Polymethine dyes selected from which can be used in my invention comprise those of formula I those rep- 2-(5. 1 mm arkn n a ieny ld e)e hy b n ml I 2-(5,5 dicyapp-2,4-pentadlepylldene)fimethylbenzothiazoline Patented Nov. s, 1958,

' wherein R represents a hydrogen atom or a lower alky According to my invention, I incorporate one or more of the polymethine dyes of Formula I with one or more of the pyridine bases of Formula II in a photographic silver halide emulsion. My invention is particularly directed to the ordinarily employed gelatino-silver-halide emul- 'sions. However, my supersensitizing combinations can be employed in silver halide emulsions in which the carrier is other than gelatin, e. g., a resinous substance or cellulosic material which has no deteriorating eifect on the silver, halide.

My invention is primarily directed to the ordinarily employed gelatino-silver-halide developing-out emulsions, e. g., gelatino-silver-chloride, -chlorobrornide, -chloroiodide, -chlorobromiodide, -bromide and -bromiodide developing-out emulsions. While the results in the following examples were obtained using gelatino-silverbromiodide emulsions, useful results have also been obtained using gelatino-silver-chlorobromide emulsions. Particularly improved sensitizing activity has been obtained in gelatino-silver-bromiodide emulsions of the developing-out type. Emulsions which form the latent image mostly inside the silver halide grains, such as the emulsions set forth. in U. S. Patent 2,456,956, dated December 21, 1948, can also be employed in practicing my invention.

The emulsions prepared in accordance with my invention can be coated in the usual manner on any suitable support, e. g., glass, cellulose nitrate film, cellulose acetate art.

film, polyvinyl acetal resin film, glycol terphthalate film,

polystyrene film, paper, metal, etc.

The polymethine sensitizing dyes of Formula I and v represented by Formula II above have little or no sensitizing action on the emulsions.

The optimum concentration of a sensitizing dye can be determined in a manner well known to those skilled in the art by measuring the sensitivity of a series of test portion of the same emulsion, each portion containing a different concentration of the sensitizing dye. The optimum concentration of my supersensitizing combinations can, of course, be readily determined in the same manner, by measuring the sensitivity of a series of test portions of the same emulsion, each portion containing a different concentration of the sensitizing dye used in the combination. In determining the optimum concentration for the supersensitizing combination, it is advantageous to employ, at first, a concentration of the sensitizing dye somewhat less than its optimum concentration. The concentration of the dye can then be increased until the optimum concentration suitable for use in the combination is determined.

Ordinarily, the optimum or near optimum concentration of the dyes selected fromthose represented by Formula I above which I employ in practicing my invention is of the order of from 0.05 to 0.30 gram per mol. of silver halide in.the emulsion.

The pyridine bases selected from those represented by Formula II above are advantageously employed in concentrations on the order of from 10.0 to 50.0 grams per mol. of silver halide in the emulsion.

Generally speaking, the concentration of the dye of Formula I to the pyridine base of Formula II can vary rather widely in my combinations, e. g., from 1:30 to 121000 (by weight) in many cases.

The methods of incorporating sensitizing dyes in photographic emulsions are well known to those skilled in the In practicing my invention, the sensitizing dyes can be directly added to the emulsions, or they can be added to the emulsions in the form of their solutions. Advantageously, the sensitizing dyes of Formula I can be dissolved in an appropriate solvent, such as acetone, methanol, etc., and these olutions added to the photographic emulsions. Since the pyridine bases of Formula II are liquids and are compatible with the photographic emulsions, the sensitizing dyes of Formula I can frequently be dissolved in these pyridine bases and the resulting solutions added to the emulsions. Alternatively, a solution of the sensitizing dyes of Formula I in a solvent other than the pyridine bases-can be intermixed with the pyridine bases before addition to the emulsion, and this mixture added in the usual manner. The sensitizing dyes and pyridine bases of my invention are advantageously incorporated in the finished, washed emulsions and should be uniformly distributedthroughout the emulsions. The following procedure is satisfactory: Stock,so-'

lutions of the sensitizing dyes described above are preemulsion Stirring is continued until the vdye (or dyes)- is thoroughly incorporated in the emulsion. Then, the desired amount of the pyridine base is slowly added to theemulsion, while stirring. If desired, the pyridine base can be added prior to the solution of sensitizing dye (or dyes), or a mixture of these two ingredients can'be added 'in a single operation. arately added, stirring'is continued until all ingredients have been uniformly dispersed throughout the emulsions. The supersensitized emulsion can then be coated out on a suitable support, such as glass, cellulosenitratefilm, cellulose acetate film, polyvinyl acetal resin film, paper, etc., to a suitable thickness and allowed to dry. The details of such coating methods are well known to those skilled in the art.

The amounts of sensitizing dye and pyridine'base actually incorporated in the' emulsion will vary somewhat,

from case to case, according to the emulsion employed, particular sensitizing dye and pyridine base employed, and according to the effect desired. The regulation and adoption of the most economical proportions will be ap parent to those skilled in the art upon making the ordinary observations and tests customarily employed in the art. Accordingly, the foregoing procedures and proportions are to be regarded only as illustrative.

invention is directed to any emulsion containing a com- The following examples will serve to illustrate further the manner of practicing my invention: To different proportions of the same batch of photographic gelatinosilver-bromiodide emulsion were added (1) a sensitizing dye selected from those of Formula I above and (2) a combination of the sensitizing dye of Formula I and a pyridine base, such as those represented by Formula II above. No data on the coating containing the pyridine base of Formula II alone are given, inasmuch as'it has been found that these compoundshave little or no measureable sensitizing action of their own when so employed in these emulsions. While different emulsion batches were employed in some of these examples, the same emulsion batches were employed for the coatings in each individual example.

were digested for a short time in a tank maintained at about 52 C. The different portions of emulsion were then coated on the supports and exposed in the usual When the two ingredients are sep- Clearly, myv

Before coating out the emulsions on the support, the emulsions containing the addendamanner in a spectrograph and a sensitometer (Type Ib) througha filter as identified in the following table. The 30/,E speed, gamma and fog obtained after development of V the exposed emulsions are given below. The de- 8 urements for these emulsions are givenjn Example ,9 of the above table. T In Figure 2, curve C represents the sensitivity of an ordinary gelatino-silver-bromiodide emulsion sensitized veloper employed had the following composition: 5 with 2-(5,5-dicyano-2,4-pentadienylidene) 3 methyl- G benzothiazoline, while curve D represents the sensitivity N th 1 h n 1 If t 6 of the same emulsion sensitized with 2-(5,5-dicyano- 2, 4-

g ammop c o a e pentadienylidene)-3-methyl benzothiazoline and pyridine.

g ?g "HE The sensitometric measurements for these emulsionsare i Su (an y g 10 given in Example f the above table.

p car (male mono y rate In Figure 3, curve E represents the sensitivity of an potassmm bromlda. "r ordinary gela-tino-silver-bromiodide emulsion sensitized water to make one liter with 2(5,5-dicy-ano 2,4 pentadienylidene) 1 ethyl B- Wratten No. 12 filter transmits substantially no light naphthothiazoline, while curve F represents the sensitivof wavelength shorter than about 495 mu, Wratten No. 15 ity of the same em 56118412611 With y filter transmits substantially no light of wavelength pe y yl-B- p n shorter th about 530 mu and wratten No, 53 filt pyridine. The sensltometrlc measurements for these transmits only light of wavelengths lying between 465 emulslons are glvgn in Example 7 offlle above tablearid 620 mu. Photographic silver halide emulsions, such as those The filter used in the examples below were le ted o 20 listed above, containing the supersensitizing combinations that they transmitted light in the region in which the senof my invention can also contain such addenda as chemisitizing dyes had their maximum sensitivity. cal sensitizers, e. g., sulfur scnsitizers (e. g., allyl thio- Without Base With Base Dye No. Exposure Example (gJmol. Base Filter AgX) (cc./mo1. AgX) /E 30/E No.

Speed Gamma F0" Speed Gamma Fog 1. (08).--. Pyridine nil 1111 .00 7.2 2.04 .10 25 2. (08).-.- do 3.20 .10 104 2. 04 .11 25 a. 8) 1.05 .00 27.5 3.04 .00 12 4. 2. 40 .07 90 3.00 .09 12 5. nil .07 40.5 2.00 .09 12 0. nil .07 40.5 2. 90 .00 12 7. 2.80 .09 220 3.40 .11 12 s. 3.54 .07 117 3.40 .09 12 9. 1.8 .00 11.4 2.0 .00 5s 10. 2. 40 .00 17.3 2.68 .00 5s 11. 2.08 05 15.8 2. 00 58 12. nil .04 15.8 2. 42 07 12 13. 2. 02 00 0. 25 2. 90 00 12 14. 2. 42 00 1. 09 2. 52 00 12 15. 2. 50 00 3.85 2. 50 07 12 10. 2. 20 .05 .72 2.00 07 12 17. 3. 0 .09 30. 5 2. 0s 10 12 1s. 2. 5 .10 117 2. 59 11 12 19. 1. 4s 00 0. 9 2. 54 07 12 20. 2. s 07 182 2. 0 07 12 In a manner similar to that illustrated in the above table, other polymethine dyes represented by Formula I above can be employed in combination with various pyridine bases, such as those represented by Formula II above to advantage.

I have also found that compounds corresponding to those of Formula I above, except that one of the cyano groups is replaced by a carbalkoxyl group, can be employed in combination with the pyridine bases of Formula II. Such derivatives of the compounds of Formula I are shown in U. S. Patent 2,638,473, U. S. Patent 2,697,707 and Belgian Patent 506,549.

'The accompanying drawing illustrates the supersensitizing effect obtained with three of my new combinations of polymethine dyes and pyridine bases in gelatino-silverbromiodide emulsions. Each figure of the drawing is a diagrammatic reproduction of two spectrograms. In each figure, the sensitivity of the emulsion containing only the polymethine dye of Formula I is represented by the solid curve. The sensitivity of the emulsion containing both the polymethine dye of Formula I and the pyridine base of Formula II is represented by the curve consisting of short dashes. No curve showing the sensitivity of the emulsion containing the pyridine base of Formula II is shown, since these compounds have no measureable effect on the emulsion employed.

In Figure 1, curve A represents the sensitivity of an ordinary gelatino-silver bromiodide emulsion sensitized with 2-(3,3-dicyanoallylidene) 3 ethylbenzothiazoline, while curve B represents the sensitivity of the same emulsion sensitized with 2-( 3,3-d1'cyano-ally1idene)-3-ethylbenzothiazoline and pyridine. The sensitometric measa carbamide, thiourea, allylisothiocyanate, cystine, etc.), various gold compounds (e. g., potassium chloroaurate, auric trichloride, etc.) (see U. S. Patents 2,540,085; 2,597,856 and 2,597,915), various palladium compounds, such as palladium chloride (U. S. 2,540,086), potassium chloropalladate (U. S. 2,598,079), etc., or mixtures of such sensitizers; antifoggants, such as ammonium chloroplatinate (U. S. 2,566,245), ammonium chloroplatinitc (U. S. 2,566,263), benzotriazole, nitrobenzimidazole, S-nitroindazole, benzidine, mercaptans, etc. (see Mees- The Theory of the Photographic Process, Macmillan Pub., 1942, page 460), or mixtures thereof; hardeners, such as formaldehyde (U. S. 1,763,533), chrome alum (U. S. 1,763,533), glyoxal (U. S. 1,870,354), dibromacrolein (Br. 406,750), etc.; color couplers, such as those described in U. S. Patents 2,423,730, Spence and Carroll U. S. Patent 2,640,776, issued June 2, 1953, etc.; or mixtures of such addenda. Dispersing agents for color couplers, such as those set forth in U. S. Patents 2,322,027 and 2,304,940, can also be employed in the above-described emulsions.

Many of the polymethine dyes represented by Formula I above can be prepared according to known methods. For example, U. S. Patent 2,697,707, issued December 21, 1954, describes the preparation of certain of these dyes. French Patent 1,099,380, granted March 16, 1955, and corresponding Belgian Patent 519,732, granted May 30, 1952, also describe the preparation of certain of these polymethine dyes. Belgian Patent 506,549, granted No vember 14, 1951, also describes the preparation of certain of these polymethine dyes.

The following examples will serve to illustrate further 245-246 C. with decomposition.

.9 a the preparation of certain of the polymethine dyes represented by Formula I above which can be employed in'm invention to advantage.

Example A.2-(3,3-dicyanoallylidene) 3 ethylbenzoxazoline Example B.-2-(5,5-dicyono-2,4-pentadienylidene)-1 ethylnaphtho-[1,2lthiazline A mixture of 5.26.g. (1 mol.) of 2 (4-acetanil ido-1,3- butadienyl)-1-ethylnaphthoE1,21thiazolium iodide, 3.3 'g; (1 mol. plus 400% excess)of malononitrile, ml. of ethyl alcohol and 1.01 g. (1 mol.) of triethylamine was heated at the refluxing temperature for 10 minutes. After chilling, the. solid was collected on a filter and washed with methyl alcohol. The yield of product was 30% crude and 19% after two purifications, each of which con' sisted of dissolving the crystals in 50 ml. of hot pyridine,

filtering the solution and then adding 150 ml. of methyl alcohol to the filtrate. The dark bluish crystalsfhad M. P. 278-279 C. with decomposition.

' 2-(5,5-dicyano-2,4- pentadienylidene) 3 ethylbenzo thiazoline was prepared, in like manner, by using 4.76 g. (1 mol.) of 2-(4-acetanilido-1,3 butadienyl) -3-ethylbenzothiazolium iodide in place of the 2-(4-acetanilido- 1,3 -butadienyl) -1-ethylnaphthol 1,2] thiazolium iodide in the above example. The yieldof product was 43% crude and 30% after two purifications, each of which consisted of dissolving the crystals in 50 ml. of hot pyridine, filtering the solution and then adding 300 ml. of methyl alcohol to the filtrate- The felt of steel blue needles had M. P.

1 Dye 2 was prepared in the manner shown inExarnple B above and was obtained as a solid melting at 250-251 C. with decomposition. Dye 4 was obtained as a solid melting at 194-195 C. with decomposition. Dye 9'was obtained as a solidmelting at207 208 'C. with decomposition. Dye 10 was obtainedas a solid melting at 212 -213 C. with decomposition. Dye l7 was'obtained as. a solid melting at 225 226 C. 'with" decomposition. Dye 18 was obtained as a solid melting at 273-274" C. with decomposition. 'Dye 20 was obtained as a 'solid melting at 301-302 C. with decomposition.

The polyniethine dyes of my invention represented by Formula I abovewherein R and R together. represent an .alkylene group can be prepared according to the method described in U. S. Patent 2,697,707 (corresponds to British 704,770 and 704,840). The following examples illustrate thismethod. 1

Example 'c.-'-1-ditana ah iene-z weih i-z 3H) benzothiazolylidene)cyclopentane A mixture of 18.35 g. (1 mol.) of 3-methyl-2-methyl mercaptobenzothiazolium p-toluenesulfonate, 13.2 g. (1 mol. plus excess) of l-dicyanomethylenecyclo pentane, 35 ml. of absolute ethyl alcohol and 5.05 g. (1 mol.) of triethylamine was heated at the refluxing temperature of 20 minutes. After chilling, the solid was collected on a filter and washed with methyl alcohol. The yield of product was 89% crude and 69% after two recrystallizations from ethyl alcohol. The red crystals had M. P. 208 209 C. with decomposition.

1-dicyanomethylene-2-(3-ethyl-2(3H) -,benzothiazolylidene)cyclopentane was prepared in like manner, by using.

17.45 g. (1 mol.) of 3-ethyl-2-ethylmercaptobenzoe thiazolium ethylsulfate in place of the 3-methyl-2-methylmercaptoben'zothiazolium p-toluenesulfonate in the above example. The yield of product was 51% crude and 43%. after two recrystallizations from methyl alcohol. .The red crystals hadrM. P. 226-227 C. with decomposition.

Example D.1-dicyz znomethylene-2-(3-methyl 2(3H)- V benzoxazolylidene)cyclopentane Hz 0 H O CH CN I 1 C=CO=O\ CN A mixture of 8.25 g. (1 mol.) of 2-methylmercaptobenzoxazole and 9.3 g. (1 mol.) of methyl p-toluenesulfonate was heated over a free flame until bubbles appeared and then the reaction mixture was stood at room temperature. The resulting quaternary salt, 6.6 g. (1 mol.) of l-dicyanomethylenecyclopentane, 35 ml. of absolute ethyl alcohol and 5.05 g. (1 mol.) of triethylamine was heated at the refluxing temperature for 20 minutes. After chill ing, the solid was collected on a filter and washed with methyl alcohol. The yield of product was 34% crude and 27% after two recrystallizations from methyl alcohol. The orange-yellow needles had M. P. 197-198 C.

Example E.1-dicyan0methylene-2- (3-methyl-2 (3H) benzothiazolylidene) cyclohexane H2O CH2 I C=O CH2 1 o N H on ON O tions from ethyl alcohol. The scarlet needles had Pg 220-221 C. with'decompositio'n.

After chilling, the solid was collected on a- A mixture of 45.0 g. (1 mol.) of Z-fl-acetanilidovinyl- B-ethylbenzothiazolium iodide, 26.4g. (1 mol. plus 100% excess) of 1-dicyanomethylenecyclopentane, 100 ml. of absolute ethyl alcohol and 10.1 g. (1 mol.) oftriethylamine was heated at the refluxing temperature for 30 minutes. The cool reaction mixture was stirred with cold water. After chilling, the solid was collected on a filter and Washed with water. The residue was transferred to a beaker and stirred with hot methyl alcohol. After chilling, the suspension was filtered. The residue was stirred with hot methyl alcohol and the suspension was filtered hot. The yield of product was 13% crude and 11% after two recrystallizations from pyridine. The dark crystals 'with a green reflex had M. P. 250-252 C. with decomposition. Dye 19 was prepared =in the same manner as the dye of Example Aand was obtained as a solid melting at 228-229 C.

The term lower alkyl as used herein means an alkyl group containing from 1 to 2 carbon atoms.

What I claim as my invention and desire secured by Letters Patent of the United States is:

1. A photographic silver halide emulsion sensitized with a supersensitizing combination of at least one dye selected from those represented by the following general formula:

wherein R represents an alkyl group containing from 1 to 2 carbon atoms, R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms and groups which, together with R represent the atoms necessary to complete a cycloalkane ring containing from 5 to 6 carbon atoms, R when R represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms, represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms, an alkoxyl group containing from 1 to 2 .carbon atoms, a monocyclic aryl group of the benzene series and a thienyl group, n represents a positive integer of from 1 to 2, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus selected from the group consisting of those of the benzothiazole series, those of the naphthothiazole series, those of the benzoxazole series, those of the naphthoxazole series, those of the bcnzoselenazole series, those of the naphthoselenazole series, those of the thiazoline series, those of the benzirnidazole series, and those of the 3,3-dialkylindolenine series, and at least one pyridine base selected from those represented by the following general formula:

wherein R represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms. 1

I 2. A photographic silver halide emulsionas defined in claim 1 wherein the silver halide is silver-bromiodideand wherein the pyridine base is pyridine. i

A Photographic ve h lidecmulsion s nsitized 12 witha-supersensitizing combination of at least one dye selected from those represented by the following general formula:

wherein R represents an alkyl group containing from 1 to 2 carbon atoms, R 'represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms and groups which, together with R represent the atoms necessary to complete a cycloalkane ring containing from 5 to 6 carbon atoms, ,R-,,, when .R represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms, represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2carbon atoms, an alkoxyl group containing from 1 to 2carbon atoms, a monocyclic aryl group of the benzene'series and a thienyl group, n represents a positive integer of from *1 to 2, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the benzothiazole series, and at least onepyridine base selected from those represented by the following general formula:

wherein .R represents an alkyl group containing from 1 to 2 carbon atoms, R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from l to 2 carbon atoms, an alkoxyl group containing from 1 to 2 carbon atoms, a monocyclic aryl group of the benzene series, and a Z-thienyl group, and Z represents the non-metallic atoms necessary to complete a heterocyclicnucleus of the benzothiazole series.

. 5. 'A photographic gelatino-silver-halide developing-out emulsion sensitized with-a supersensitizing combination of pyridine and at least one dye selected from those represented by the following general formula:

wherein R represents an alkyl group containing from 1 to 2 carbon atoms, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus ofthe benzothiazole. series. V

6. A photographic gelatino-silver-halide developing-out emulsion sensitized with a supersensitizing combination of 2-(5,5-dicyano-2,4-pentadienylidene) 3 methylbenzothiazoline andpyridine.

7. A photographic silver halide emulsion sensitized with a supersensitizing combination of at least one dye selected from those represented bythe following general formula:

whereinR represents an alkyl group containing from t 1 to 2 carbon atoms, R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms and groups which, together with R,,-represent the atoms necessary to complete a cycloalkane ring containing from 5 to 6 carbon atoms, R when R represents a member selected from the group. consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms, represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms,

analkoxyl group containingfrom 1 to 2 carbon atoms, a monocyclic aryl group of the benzene series and a thienyl group, n represents a positive integer of from 1 to 2, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the benzoxazole series, and at least one pyridine base selected from those represented by the following general formula:

wherein R represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms. 7

8. A photographic gelatino-silver-halide developing-out emulsion sensitized with a supersensitizing combination of pyridine and at least one dye selected from those represented by the following general formula:

,z. n-rr--b=on-cn=cn-c=o wherein R represents an alkyl group containing froml to 2 carbon atoms, R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms, an alkoxyl group containing from 1 to 2 carbon atoms, a monocyclic aryl group of the benzene series, and a Z-thienyl group, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the benzoxazole series.

9. A photographic gelatino-silver-halide developing-out emulsion sensitized with a supersensitizing combination of pyridine and a dye selected from those represented by the following general formula:

-out emulsion sensitized with a supersensitizing combina-' tion of 2-(5,S-dicyano-4-methyl-2,4-pentadienylidene)-3- ethylbenzoxazoline and pyridine.

11. A photographic gelatino-silver-halide developingout emulsion sensitized with a supersensitizing combination of pyridine and at least one dye selected from those represented by'the following general formula:

wherein R represents an alkyl group containing from 1 to 2 carbon atoms, R represents a 2-thienyl group and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the benzoxazole series.

12. A photographic gelatino-silver-halide developingout emulsion sensitized with a supersensitizing combination of 2-[5,5-dicyano-4-(Z-thienyl)-2,4-pentadienylidene]-3-ethylbenzoxazoline and pyridine. I

13. A photographic silver halide emulsion sensitized with a supersensitizing combination of at least one dye 14 selected from those formula: a

n- -rf b(=oHcH .-i=c-o=o wherein R represents an alkyl group containing from 1 to 2 carbon atoms, R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms and groups which, together with R represent the atoms necessaryto complete a cycloalkane ring containing from 5 to 6 carbon atoms, R when R represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms, represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms, an alkoxyl group containing from 1 to 2 carbon atoms, a monocyclic aryl group of the benzene series and a thienyl group, n represents a positive integer of from 1 to 2, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the naphthothiazole series, and at least one pyridine base selected from those represented by the following general formula:

wherein R represents a member selected from the group taining from 1 to 2 carbon atoms.

14. A photographic gelatino-silver-halide developingout emulsion sensitized with a supersensitizing combination of pyridine and at least one dye selected from those represented by the following general formula:

wherein R represents an alkyl group containing from 1 to 2 carbon atoms, R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms, analkoxyl group containing from 1 to 2 carbon atoms, a monocyclic aryl group of the benzene series, and a 2-thienyl group, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the naphthothiazole series.

15. A photographic gelatino-silver-halide developingout emulsion sensitized with a supersensitizing combination of pyridine and at least one dye selected from those represented by the following general formula:

wherein R represents an alkyl group containing from 1 to 2 carbon atoms, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the naphthothiazole series.

16. A photographic gelatino-silver-halide developing- I out emulsion sensitized with a supersensitizing combination of 2-(5,5-dicyano-2,4-pentadienylidene)-1-ethyl[1,2]- naphthothiazoline and pyridine.

17. A photographic gelatino-silver-halide developingout emulsion sensitized with a supersensitizing combination of pyridine and at least one dye selected from those represented by. the following general formula:

I 1 R-N represented by the following general' 15 ofihe benzene series, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus ref-the napthothiazole series.

18. A photographic gelatino-silver-halide developingout emulsion sensitized with a supersensitizing combination of 2- (5,5-dicyano-4-pheny1-2,4-pentadieny1idene)-1- methyl[1,2 ]naphthothiazoline and pyridine.

References Cited in the file of this patent UNITED STATES PATENTS Carroll et a1 Apr. 23, 1946 in 1 6 2,478,369 Carroll et a1 Aug. 9, 1949 2,638,473 Edwards May 12, 1953 2,697,707 Kendall Dec. 21, 1954 5 FOREIGN PATENTS 519,732 Belgium May 30, 1953 OTHER REFERENCES Mees: The Theory of the Photographic Process, re-

10 vised ed., MacMillanCQ, N. Y., 1954, pages 376 and 41s. 

1. A PHOTOGRAPHIC SILVER HALIDE SMULSION SENSITIZED WITH A SUPERSENSITIZING COMBINATION OF AT LEAST ONE DYE SELECTED FROM THOSE REPRESENTD BY THE FOLLOWING GENERAL FORMULA: 